1. Field of the Invention
The present invention relates to an engine control system for controlling a current supply to an ignition coil and a fuel injection of an engine.
2. Description of the Related Background Art
In an engine control system, when a timing to supply a current to an ignition coil or an ignition timing for allowing a spark plug to discharge a spark, a rotational angle position from a reference position of a crankshaft of an engine, that is, a crank angle is detected and those timings are set on the basis of the crank angle (for example, JP-A-63-263269 and JP-B-5-11562).
In order to detect an angle of a crankshaft of an engine, a disk-shaped rotary body which rotates in response to the rotation of the crankshaft and an electromagnetic pickup arranged near the outer periphery of the rotary body are used. A plurality of convex portions made of a magnetic material are provided as portions to be detected every predetermined angle on or near the outer periphery of the rotary body and at least one of the convex portions is missing. When the rotary body rotates in association with the crankshaft and the convex portion passes near the electromagnetic pickup, a pulse is generated from the electromagnetic pickup. A relatively long period in which no pulse is generated due to the missing of the convex portion occurs. By measuring such a period, it is assumed that a time point of a pulse to be generated next shows a reference position time point of a rotational angle of the crankshaft, and a stroke of each cylinder is specified on the basis of a reference position time point.
A time from the reference position time point of the crankshaft until an engine control start time point in response to the pulse generated from the pickup at an angle position of every predetermined angle, for example, until a time point when the current supply is started, or a time until a time point to stop the current supply and allow the spark plug to discharge a spark, and further a time until a start time point of a fuel injection are measured.
In a conventional engine control system, however, since there is a period of time in which no pulse is generated from the pickup due to a missing of the portion to be detected such as a convex portion of the rotary body even when the angle position of the crankshaft is at the angle position of every predetermined angle from the reference position time point, if there is an engine control in which the start time point of time measurement should be set at an angle position time point of the crankshaft in such a period, the measurement of time until the engine control start time point cannot be started. The engine control start time point is, therefore, set earlier and there is a problem such that a proper engine control cannot be performed.